Genetic stock structure of the silky shark Carcharhinus falciformis in the Indo-Pacific Ocean.

Abstract

The silky shark, Carcharhinus falciformis, is a cosmopolitan species commonly caught as a bycatch for longline fisheries. However, the genetic stock structure for the Indo-Pacific Ocean is not well-defined yet. Here, we used eight microsatellite loci to examine the genetic stock structure and effective population size of 307 silky sharks across 5 Indo-Pacific sampling locations. A major genetic break was found between Aceh and the remaining locations (FST = 0.0505-0.0828, p = 0.001). The Indian Ocean displayed a slightly lower effective population estimate (Ne) compared to the Pacific Ocean, potentially due to the higher fishing pressure in the Indian Ocean region. The lowest Ne was found in the Aceh population (Ne = 2.3), suggesting it might be a small and endemic population. These findings offer valuable information for the conservation and management of the silky shark. We suggest that the population around Aceh waters constitutes a distinct stock and should be managed independently. Further investigations into migratory and movement patterns are needed to define the boundaries of different stocks, ensuring effective management the silky shark across the Indo-Pacific region.